The present disclosure relates generally to liquid crystal displays (LCDs) and, more specifically, to techniques for controlling the slew rate of gate driving signals for LCDs.
This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present techniques, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
Display devices are commonly used in conjunction with or as a component of an electronic device to provide visual feedback to a user. One type of display is a liquid crystal display (LCD), which typically includes rows and columns of thin-film-transistors (TFTs) arranged in an array adjacent a layer of liquid crystal material, wherein the TFTs represent image pixels. The LCD may be configured to selectively modulate the amount and color of light passing through each of the pixels by a varying an electric field associated with each respective pixel to control the orientation of the liquid crystals. By controlling the amount of light that may be emitted from each pixel, the LCD, in conjunction with a color filter array, may cause a viewable color image to be displayed.
During operation of an LCD, the gate of a TFT associated with a pixel may be switched on upon receiving a gate activation signal provided by a gate driver circuit. When the TFT is switch on, a data voltage applied to the source of the TFT may be stored as a charge in a pixel electrode coupled to the TFT. By way of example, the TFTs within the pixel array may be switched on sequentially one row at a time, and image data corresponding to a selected row may be sent to the pixels of the selected row when it is activated. When the gate activation signal transitions to cause a TFT of the selected row to switch between on and off states, rise and fall transition time properties (e.g., slew rate) of gate activation signal may influence and affect channel charge distribution behavior of the TFT. For instance, when a TFT is switched from an on state to an off state, charge remaining in the channel of the transistor is redistributed between a corresponding pixel electrode and source line.
To improve image quality, it may be desirable to cause more of the remaining channel charge to be distributed to the source line rather than the pixel electrode. The portion of the channel charge distributed to the pixel electrode, which may be referred to as an error charge, may sometimes result in voltage kickback errors occurring at the pixel. Generally, the amount of error charge distributed to the pixel electrode is proportional to the slew rate of the gate activation signal applied to the TFT. Thus, as the slew rate, which may be expressed as a change in volts per unit of time (e.g., milliseconds, microseconds, nanoseconds, etc.), of the gate signals increases (e.g., becoming faster and resulting in shorter rising/falling transition times), more error charge may be distributed to the pixels of the LCD, which may cause certain visual artifacts, such as flicker, to occur more frequently and/or severely due to the effects of voltage kickback error. Such artifacts may be perceived as aesthetically unpleasing to a user viewing an image on the display. For slower slew rates, more of the channel charge may be redistributed to the source line than to the pixel electrode, which may help to reduce artifacts caused by the effects of voltage kickback. Accordingly, for at least the reasons discussed above, it may be desirable to design and provide an LCD display that is capable of regulating or otherwise setting the slew rate of gate activation signals supplied to TFTs, such that excess channel charge is distributed between source lines and pixel electrodes in a way that reduces the effects of voltage kickback errors and improves image quality.